As it is generally known, most traditional firearm ammunition cartridges are constructed using a metal shell casing (e.g. a brass casing). The metal casing of a traditional cartridge typically contains some amount of propellant (e.g. gunpowder, smokeless powder, etc.) in a rearward portion of the cartridge that is sometimes referred to as the cartridge “body”. The metal casing of a traditional casing also holds a projectile in a frontward portion of the cartridge that is sometimes referred to as the cartridge “neck”. Traditional metal cartridge cases typically have a tapered shape, in which a relatively wider diameter body steps down to a relatively smaller diameter neck. When a traditional metal case cartridge is fired, the propellant contained in the metal casing is ignited. Gases resulting from the burning of the propellant pressurize radially and expand the metal casing against the wall of the chamber, and push against the base of the projectile, causing the projectile to be expelled from the front of the cartridge and through the barrel of the firearm.
In contrast to traditional metal case cartridges, cased telescoped (CT) ammunition cartridges completely encase the propellant and the projectile within a cylindrical shell. Firearms designed to fire CT ammunition provide full support for the cartridge exterior while firing. Because the firearm provides full cartridge exterior support, the case of a CT cartridge may be thinner than in traditional cartridges. By replacing the relatively thick casing used in traditional ammunition with a thinner, relatively lightweight casing (e.g. a relatively lightweight polymer casing), CT ammunition may provide a significant reduction in ammunition weight, enabling relatively larger numbers of rounds to be carried per unit weight, e.g. by infantry soldiers.